Notch filter

Thread Starter

valdo1813

Joined May 11, 2014
1
HI, thanks for your time, I'm trying to design a notch filter with a cutoff frequency of 60 hz. So I decided to use a single band pass filter 60 hz and then use an opamp to subtract the signal and thus have a notch filter, but the output instead of the desired output, I get the signal with gain 10 (wich its my gain on desing of single band pass filter) more the input signal. I hope your support and thank you very much for your time. sorry for my english im from mexico :(




red= first filter (single band pass filter 60 hz with 10 gain)
green= original signal
blue= output from substract
esquematico.png

grafica.png
 

crutschow

Joined Mar 14, 2008
34,285
The bandpass amp has positive feedback so I don't see how that can work.

Note that when subtracting the two signals you need to account for the phase-shift that the bandpass filter generates, which affects the subtraction result.
 

#12

Joined Nov 30, 2010
18,224
Thanks. I couldn't see how to fix what's wrong with that, so I just posted some images of circuits that will probably work.
Valdo: You might describe what your end goal is and receive some good information.
 
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